Programming scale engine starts.

[Tench745]

I was watching a video of engine starts recently and I thought it would be cool to have a scale looking engine start for my Dumod.
I have a Taranis X9D+ and would like to figure out how to program it so that the left motor turns very slowly for a bit, then kicks faster a couple times like each cylinder is starting to fire, until finally settling into a low idle, then the right motor does the same. I already have a throttle cut programmed to a 3 position switch. Down is off, middle would be regular throttle control, and switching it to the final position could initiate the startup procedure and then keep the motors at a low idle. I have differential thrust programmed in already, so each motor is already on its own channel.
I would appreciate any guidance you open TX pros could give. @rockyboy @willsonman @RCdiy @PsyBorg ? Who else am I missing?
The way I see it there are two phases.
1) The startup sequence
Must run once when the switch is flipped, but not after the motors are running.

2) Low idle
The motors hold a constant speed when the switch is in the up position and the startup has run once.

 

[Tench745]

I’ve already begun rethinking this idea. Perhaps the middle position should run the startup and then idle, but would activate only when the throttle stick is moved off zero.

 

[L Edge]

It is interesting to see what other radios can do. Especially trying to start the motor slowly, then kicks faster and then the idle.

I ended up starting a low idle speed on one motor, wait 5 secs, then the other one starts.
Having only 2 sequencers, also set up a brake on the nose wheel. 3 positions 1) brake is on for startup 2) brake is full off for takeoff 3) servo oscillates so the rod touches the wheel is off-on-off so the transport taxis with slow speed.
Could also be used to rotate a gun turret for scale effects.

It was a nightmare learning how to get the sequencer to work. Good luck, will be watching.

 

[Tench745]

Played with this a little more today. I still don't know what I'm doing. I figured out how to program a low idle on a switch and delay the start of motor 2. I don't love that the differential thrust can shut down a motor, but I do want to still have yaw control at full throttle, so I would somehow have to mix the throttle setting into the differential thrust. Edit: Stored the throttle setting as a Gvar, then used the inverse of this for the differential value on the rudder-to-throttle mix.

I looked at using a timed logic function to create a cyclic throttle setting. It sort-of worked, but once motor two started they cycled together. I would need to figure out how to stop the cycle on the first motor before the second starts. Probably more logic switches...

 

[L Edge]

What Tx brand do you have? I used the sequencer on the Spektrum DX9.
Procedure:
1) Flip switch---Left engine starts--idles about 10% rpm
2) wait 5 secs in the loop
3) Right engine starts and idles about 10% rpm
4) now both throttles work together, go fly
5) land, idle engine, to shut off, flip switch-
6) right engine shuts down, waits 5 sec, left engine shuts off.

Problem I am having is throttle cut for safety sake. It cuts the throttle, it waits 5 sec, and then cuts second engine. Working on that. Bad if one engine goes out in flight.

I just finished the brake system for my transport. 3 positions

Switch position 0 BRAKE is on (going to used start engine sequence)

Switch position 1 Idle engines or add some rpm's and start taxiing with oscillating brake to give fixed taxi speed. I also added rotary pot to adjust tension on the wheel.

Switch position 3 Brake off totally to take off runway.

Reverse sequence to land and shut off engines.

 

[Tench745]

What Tx brand do you have? I used the sequencer on the Spektrum DX9.
Procedure:
1) Flip switch---Left engine starts--idles about 10% rpm
2) wait 5 secs in the loop
3) Right engine starts and idles about 10% rpm
4) now both throttles work together, go fly
5) land, idle engine, to shut off, flip switch-
6) right engine shuts down, waits 5 sec, left engine shuts off.

Problem I am having is throttle cut for safety sake. It cuts the throttle, it waits 5 sec, and then cuts second engine. Working on that. Bad if one engine goes out in flight.

I just finished the brake system for my transport. 3 positions

Switch position 0 BRAKE is on (going to used start engine sequence)

Switch position 1 Idle engines or add some rpm's and start taxiing with oscillating brake to give fixed taxi speed. I also added rotary pot to adjust tension on the wheel.

Switch position 3 Brake off totally to take off runway.

Reverse sequence to land and shut off engines.

I'm using a FrSky Taranis X9D+. I have my throttle cut on a 3-way switch. The first positon overrides throttle to -100% no matter what else is programmed in. The second position activates the throttle stick. The third position starts the sequencer and runs the engine start and idle. If I flip back to the second position it will stop one motor then the other.

 

[L Edge]

I'm using a FrSky Taranis X9D+. I have my throttle cut on a 3-way switch. The first positon overrides throttle to -100% no matter what else is programmed in. The second position activates the throttle stick. The third position starts the sequencer and runs the engine start and idle. If I flip back to the second position it will stop one motor then the other.

Understand second position activates throttle control. Third position, the sequencer is in control and does half of it where it gets both engines going at idle. By flipping your switch to position 2, it activates your control after it finishes out of the sequencer.

Mine, the sequencer finish 1/2 (both engines are at idle) and gives you throttle to fly. After flying and landing, it is only after you flip the switch on the sequencer back and it shuts the engine down one, waits 5 sec and then the other.

All I am saying is that I built within the sequencer 1/2 cycle that after both engines are idle, it gives you control of the throttle from idle to full power. In order to stop the engines one at a time with the wait cycle is after you land, you need to flip the switch and complete the other half cycle.

 

[tamuct01]

This is a neat idea. Unless you have a very large model, I would think that getting a scale-looking startup with an electric motor will be difficult. I think that even at low speeds the electric motors spin way too fast to look scale. The ESCs I have seem to jump from stopped to "idle" speed with no in between. Good luck! I think you're on the right path with the Taranis.

 

[Taildragger]

Brushed motors could work well for this